OK rhizo_1
Why do you need sunlight. Weed seeds need heat and moisture to germinate. Having germinated there is no light to enable photosynthesis so the weed dies off. Just what you need isn't it?
As to air exchange, thats assuming you seal down all edges, which is almost impossible. Just try keeping large sheets of plastic down in a high wind! But what it does achieve is a complete lack of snow compression, which doesn't pack the ground down again requiring a spring tilling.